Improvement in hydraulic drawbacks



srTED STATES PATENT OEEIioE COLEMAN SELLERS, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO WILLIAM SELLERS, OF SAME PLAGE.

IMPROVEMENT IN HYDRAULIC DRAWBACKS.

Specification forming part of Letters Patent'o. 178,965, dated June 20, 1876; application filed December 7,- 1874. v

To all whom t may concern:

Be it known that I, COLEMAN SELLERS, ofthe city and county of Philadelphia, and State of Pennsylvania, have invented al1 Improvement in Hydraulic Drawbacks, of which the following-is a specification:

In hydraulic drawbacks, as heretofore constructed, the fluid-pressure is exerted continuously upon one side of a small piston connected to the pressure-ram in such a manner that when the pressure is withdrawn from the ram upon the completion of its stroke the continuous pressure upon the small piston will draw the ram back to its starting-point.l The effect of such a drawback is the same as that of a counter-weight, both detracting from the power of the machine in its forward motion by so much as is required to withdraw the ram and displacethe Water which moved it.

The object of my invention is to provide a hydraulic drawback which shall not detract fromthe power of the machine in its forward motion; and my invention consists inequaliz ing the hydraulic pressure on both sides of the drawback-piston during the forward motion of the ram, and applying the pressure to one side only-of the piston during the backward motion of the ram; 'and it further consists in attaining these conditions without increasing the number or altering` the character of the ingress and egress valves upon the machine.

The accompanying drawing, which forms a part of this specification, shows, in vertical section,two illustrationsof my improved hydraulic drawback applied to a welding, upsetting, and shaping machine, the details of which I will not describe, as they form no part of the invention herein claimed, but' constitute the subj ect-matter of separate applications, ofeven date herewith, made by Wm. Sellers, of Philadelphia, Pennsylvania, and Geo. H. Sellers, of Wilmington, Delaware.

In the drawings referred to, the section at A represents my improved hydraulic drawback applied to a horizontal cylinder-13, to a vertical cylinder; but as the construction and operation of bot-h are similar, I shall confine my description to the one represented at A. The main ram 0f the machine a, works in a cylinder lined with copper and closed at its -fin the bottom of the cylinder c.

inner end in the manner described in the Patent No. 127,191, issued'to me, May '28, 1871. hydraulic cylinder, is bored out from its outer end to form a drawback-cylindeac, of the proper diameter. This cylinder is provided with a piston, d, attached to the rear of the mainram a by means of the piston-rod e, which passes through the suitable packing'at The outer end of the cylinder c is closed by a tight-fitting cap, g, secured tothe drawback-cylinder by suitable bolts. A duct or passage, h, provides a direct communication without the intervention of any valves between an accumu-Y lator or the pumps and the cylinder c, under the drawback-piston d, so as to exert a pressure upon this piston to draw the ram a back. A duct, c', conveys the fluid to the main cylinder of the ram a, above and over the piston d, and through the drawback-cylinder c to the main cylinder, so that when the pressure is exerted upon the main cylinder the same pressure will be exerted behind the drawback- 'piston el. The duct i is connected to the accumulator or pumps through a stop and exhaust valve of any ordinary construction, or it may be provided with two independent stop-valves, but whatever the character of the valves `they must be capable of admitting the pressure to and permitting it to'escape from the main cylinder. It is evident that, as the pressure is continuously exerted upon the inner side of the drawback piston d, when the stop-valve is opened to admit l[he pressure behind this piston and upon the main ram a., the same pressure will exist upon both sides of the drawback-piston softhat the tendency to draw back will be eliminated, and the pressure upon the end of the piston-rod e,

not being counteracted, will tend to force the main ram forward, so that the whole of this ram in effect is subjected to the forward pressure without any abatement whatever from the drawback. When the exhaust-valve is 'opened to permit the escape. of the Huid through the -duct i, the constant pressure through the duct It upon the inner side of the drawback-piston d will draw the main ram c back, force out the water from its cylinder,

'Ihe plug by, which closes this end of thev as Well as from behind the drawback-piston d, and this operation Will continue so long as the exhaust-valve is open, or until thelimit of the return stroke of the ram is reached.

In sonic cases, as in portable riveting-machines, the ram is stationary and the cylinder moves forward under pressure. .The drawbackt not, therefore, restrict myself to the particular arrangement or devices described; but

What I claim' as n`eW,` and desire to secure by Letters Patent, is" i In a hydraulic drawback, a conduit which connects the inner end of the main cylinder with the outer end of `the drawback-cylinder, in combination with a conduit which connects theinner end of the drawback-cylinder with l t the accumulator or pump, substantially as and for the purpose set forth.

In testimony whereof Ihavc hereunto subscribed Iny name. i i

COLEMAN SELLERS.

Witnessesz ANDW. J. BosWELL, JUs. H. SGHWAGKE. 

